This invention relates generally to valve operating mechanisms for use in internal combustion engines, and more particularly to an oscillating rocker arm assembly having anti-friction bearings.
Conventional valve train rocker arms of internal combustion engines use various bearing means to accommodate loads. In addition to the loads generated by the rocker arms pushing the valves against the force of the valve springs, loads are generated by the oscillating motion of the rocker arms themselves. In order to achieve increased fuel efficiency and performance of internal combustion engines, anti-friction bearings with rollers have been used to support the rocker arms in place of plain bearings.
Typically, a rocker arm assembly with anti-friction bearings has a support shaft for supporting the rocker arm. The support shaft is mounted perpendicularly from a support stud extending from the head of the engine. The rocker arm is pivoted on the support shaft, which serves as an inner raceway, by means of drawn cup needle roller bearings mounted on the rocker arm. Retaining rings on the ends of the support shaft engage the cups of the bearings and limit axial movement of the support shaft relative to the rocker arm.
Such a rocker arm assembly is expensive and difficult to manufacture. The support shaft is first machined and hardened. The rocker arm is positioned over the support shaft before the bearings are mounted on the support shaft. The cups of the bearings are then press-fit into the rocker arm from opposite sides. Finally, retaining rings are mounted on the ends of the support shaft to limit axial movement of the bearings.
Much of the expense of such rocker arm assemblies is due to the need for drawn cup needle roller bearings having rollers with trunnions and the need for a machined and hardened support shaft. Additional expense is due to the numerous steps required at final assembly to the engine block. Although present rocker arm assemblies achieve increased fuel efficiency and performance, the costs associated with those assemblies have made them impractical for many applications.
The foregoing illustrates limitations known to exist in present rocker arm assemblies. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.